The US attorney general is reviewing a letter from Microsoft asking that it be allowed to publish more detail about US National Security Agency requests for user data.
The software giant suggests a gagging order is unconstitutional.
Leaked documents indicate the company has provided access to emails, Skype video calls and uploaded documents.
Microsoft has said that it only provides "specific data" after checking the legality of the requests.
It added that: "Numerous documents are now in the public domain.